one off, special case rec-en button for now. (circle may need tweaking)

In the long run we want a class hierarchy:
CairoWidget
-> ArdourWidget
-> ArdourLabel
-> ArdourButton
-> SpecialArdourButton(s)

gtk2_ardour/ardour_button.cc

@@ -290,6 +290,17 @@ ArdourButton::render (cairo_t* cr, cairo_rectangle_t *)
 			cairo_restore (cr);
 		}
 	}
+	else // rec-en is exclusive to pixbuf (tape machine mode, rec-en)
+	if ((_elements & RecButton)) {
+		const double x = get_width() * .5;
+		const double y = get_height() * .5;
+		cairo_arc (cr, x, y, get_height () *.2 , 0, 2 * M_PI);
+		cairo_set_source_rgba (cr, .0, .0, .0, 1.);
+		cairo_set_line_width(cr, 1);
+		cairo_stroke_preserve (cr);
+		cairo_set_source_rgba (cr, .95, .44, .44, 1.); // #f46f6f
+		cairo_fill(cr);
+	}
 
 	int text_margin;
 	if (get_width() < 75 || (_elements & Menu) ) {
@@ -533,6 +544,13 @@ ArdourButton::on_size_request (Gtk::Requisition* req)
 	if ((_elements & Menu)) {
 		req->width += _diameter + 4;
 	}
+
+	if ((_elements & RecButton) && !_pixbuf) {
+		assert(!(_elements & Text));
+		req->width += char_pixel_height();
+		req->height += char_pixel_height();
+	}
+
 	req->width += _corner_radius;
 }
 

gtk2_ardour/ardour_button.h

@@ -40,6 +40,7 @@ class ArdourButton : public CairoWidget , public Gtkmm2ext::Activatable
 		unused = 0x10,
 		Menu = 0x20,
 		Inactive = 0x40, // no _action is defined AND state is not used
+		RecButton = 0x80, // tenative, see commit message
 	};
 
 	static Element default_elements;